1. Field of the Invention
The present invention relates generally to a substrate of a recording head for recording inputted information such as characters, figures or the like, a recording head, a recording head cartridge, and a method of producing a substrate for a recording head. More particularly, the present invention relates to a substrate used for an ink-jet recording head that includes an electrical circuit for selectively feeding a driving signal to a plurality of recording elements arranged in a same base board.
2. Description of the Related Art
Various kinds of recording apparatuses each having a plurality of recording elements arranged in a row for recording characters, figures or the like on a recording medium have been hitherto known. In general, a recording apparatus of the foregoing type includes recording means having a plurality of recording elements and a driving integrated circuit capable of simultaneously driving a predetermined number of recording elements as a single block mounted on a same base board. With such construction, it is possible to execute arbitrary recording on a recording medium (sheet of recording paper, cloth, sheet of plastic material or the like) by arranging image data corresponding to the respective recording elements. Among conventional recording apparatuses as mentioned above, an ink jet type recording apparatus adapted to execute recording on a recording medium by ejecting ink from a plurality of ejecting ports disposed on the recording elements while generating few noisy sound without any impact induced by each recording operation makes it possible to perform each recording operation not only at a high density but also at a high speed. For this reason, a number of ink jet type recording apparatuses are utilized for an information processing system on the commercial basis. In practice, the ink jet recording apparatus is used as a printer located at an output terminal of, e.g., a copying machine, a facsimile, a computer, a word processor, a work station or the like or as a handy or portable printer to be equipped in operative association with a personal computer, a host computer, an optical disc unit, a video unit or the like. A conventional recording apparatus as mentioned above includes recording means (recording head), conveying means for conveying a recording medium, driving means for reciprocally displacing a recording head in the direction at a right angle relative to the direction of conveyance of a recording medium, and controlling means for controlling the ejection of ink from the recording head, the conveyance of a recording medium and the reciprocal displacement of the recording head with the aid of driving means. The recording head adapted to eject ink droplets from a plurality of ejection ports thereof is serially scanned in the direction at a right angle relative to the direction of conveyance of the recording medium. (i.e., in the main scanning direction) and subsequently, the recording medium is intermittently conveyed at a quantity of displacement thereof equal to the recorded width of the recording medium while no recording operation is performed. With this recording method, recording is executed in response to a recording signal by ejecting ink onto the recording medium. For this reason, the foregoing recording method is widely used as a quiet recording system capable of being practiced-at an inexpensive running cost. When a number of nozzles each adapted to eject ink therefrom are formed on the recording head along a straight line extending at a right angle relative to the direction of displacement of the recording head relative to the recording medium, recording can be executed by a quantity of width corresponding to the number of nozzles by simultaneously scanning the recording head and the recording medium. This makes it possible to perform a printing operation at a higher speed.
It should be added that a recording apparatus capable of forming a full color image with a recording head adapted to eject three or four kinds of inks mounted thereon has been put in practical use. A primary color mixing method is utilized for a color image forming apparatus of the foregoing type. Namely, each of all colors is obtainable by mixing three kinds of primary colors at a predetermined mixing rate. For example, in the case that yellow and red are mixed with each other, the resultant color is red. In addition, in the case that magenta and cyan are mixed with each other, the resultant color is blue. Thus, a various kind of color can be obtained based on the three primary colors as mentioned above. Usually, three kinds of recording heads, i.e., a yellow color recording head, a magenta color recording head and a cyan color recording head (of which mounting order is not definitely determined) are mounted on an ink jet recording apparatus adapted to form a multi-color image in accordance with a serial scanning system in the direction of displacement of the recording heads (i.e., in the main scanning direction). To improve the visual tone of a recorded multi-color image, it is desirable that a black color recording head is additionally mounted on the ink jet recording apparatus.
Each of the recording heads includes means for generating energy required for ejecting ink therefrom (hereinafter referred to as "recording element"), and moreover, requires a common electrode for distributively feeding a recording electric current to a plurality of recording elements. With this construction, it is necessary that the common electrode is disposed on a same base board adjacent to a group of recording elements having a plurality of recording elements arranged in parallel with each other. To this end, the common electrode is formed for a conventional ink jet recording apparatus in the following manner. For example, as disclosed in U.S. Pat. No. 5,212,503, a method which is practiced in such a manner that because of a necessity for disposing plural groups of recording elements in the vicinity of the edge portion of the base board, each conductor for electrically connecting each of the recording elements and the common electrode to each other is folded back at the position in the vicinity of the base board, the common electrode for feeding a recording electrical current to the recording elements is disposed at the position located inward of the base board away from plural groups of recording elements placed on the base board while extending in parallel with the end part of the group of recording elements, and the common electrode is electrically connected to a metallic film (second conductor portion) formed on the base board via through holes as well as a method which is practiced such that a plurality of recording elements, a group of functional elements for individually driving the recording elements (e.g., transistor array), and a driving integrated circuit for arranging image data corresponding to the recording elements are structurally disposed in the interior of a same base board can be noted as typical methods employable for forming the common electrode.
FIG. 1 shows one of the example of the ink-jet recording head using the same base board described above. Reference numeral 901 denotes a semiconductor substrate plate formed by a single crystal silicon. Reference numeral 902 denotes an N type semiconductor collector region. Reference numeral 903 denotes an ohmic contact region of N type semiconductor containing a high impurity concentration. Reference numeral 904 denotes a base region of P type semiconductor. Reference numeral 905 denotes a high impurity concentration, the regions 901 to 905 define a bipolar transistor 920. Reference numeral 907 denotes a boron hafnium layer as a heating resistance layer. Reference numeral 908 denotes an aluminum electrode. Reference numeral 909 denotes a silicon oxide layer as a protective layer. The regions 901 to 909 form a substrate 930 for recording head. In the layer configuration shown in FIG. 1, reference numeral 940 denotes a heating portion. A top plate 910 defines a liquid passage (ink passage) 950 in cooperation with the substrate 930.
A lot of improvements and proposals have been made with respect to the recording head having structures mentioned above. Recently, specific performance improvements have been further required in the recording head, such as attaining higher speed derivability, saving energy consumption, higher integration density, lower cost, higher reliability and high level functionality.
Accordingly, in order to provide a recording head with a reduced chip size, higher density integration of functional devices for driving electrothermal transducers, higher performances, higher recording ability and a lower cost of the structure of the recording head can be formed in the form of an MOS transistor array, as shown in FIG. 2A and FIG. 2B, for instance.
That is, the MOS transistor array comprises a P type silicon substrate, an oxide film 2, a guard ring 3, n+ drain region 4, an n+ source region 5. P type channel region 19, a source electrode 6, a drain electrode 7, and a gate electrode 8.
However, since the conventional recording head is constructed in the above-described manner, it is necessary that a functional element including a driving element array and a driving integrated circuit, a plurality of recording elements, and a second conductor portion for connecting the recording elements to each other are prepared by way of different steps. In the case that a common electrode for feeding electricity to the respective recording elements is disposed in accordance with a production process including the foregoing different steps, there arises a necessity for forming a plurality of metallic films to assume a multi-layered structure when a plurality of recording elements and various kinds of conductor portions are prepared in the form of films. In this case, an additional step of preparing the metallic films having a multi-layered structure is required, and moreover, there sometimes arises an occasion that a trouble such as short-circuit between metallic layers or the like occurs. In addition, in the case that a bias spattering process is practiced with the recording apparatus having different process conditions via a step of forming a driving integrated circuit, there sometimes arises an occasion that semiconductor properties ot the driving integrated circuit in the substrate are deteriorated. To cope with the foregoing problem, a proposal has been made with respect to a method which is practiced such that an electrical conductive layer having a comparatively small width of conductor is formed along the edge portion on the end part side of a substrate away from. a row of recording elements without any formation of metallic films having a multi-layered structure. However, this proposed method is not a desirable method because when an intensity of recording electric current is increased, there appears a problem that a magnitude of conductor resistance is undesirably increased due to a small width of conductor. Additionally, another proposal has been made with respect to a method which is intended to alleviate the foregoing problem. However, this method has a problem associated with a process including a step of patterning or the like. At any rate, any one of the aforementioned proposed methods has a factor of reducing a yielding rate of producing a recording apparatus.